Currently there are nearly 750,000 spine lumbar and cervical fusion procedures performed each year in the United States. These procedures are commonly performed to correct problems with displaced, damaged, or degenerated intervertebral discs due to trauma, disease, or aging. One of the most common of these procedures is spinal fusion, which involves removing some or the all of the diseased or damaged disc, inserting one or more intervertebral spacers to restore the natural height of the disc space, and allowing a bony bridge to form through the disc space fusing the adjacent vertebrae together. Increasingly, so-called “total disc replacement” (TDR) procedures are being utilized as an alternative to spinal fusion. Total disc replacements represent a new wave of spinal technology and generally involve implantation of mechanical devices designed to replace the functions of the intervertebral disc and thus preserve motion that is lost through a spinal fusion. While several different approaches may be used to access the target spine (the most common being anterior, posterior, and posterolateral approaches), the anterior approach is often utilized, especially for TDR, because it allows for greater exposure and a more complete excision of the damaged disc than the other common approaches.
Sometimes after a spinal fusion or TDR procedure it becomes necessary to remove and/or replace the previously implanted implant. During such revision surgeries it may be preferable, though not necessary, to access the spinal target site from a different approach than that used in the original surgery. This presents a challenge, however, when performing a revision of an anterior procedure because the implants deposited during an anterior procedure are generally too large to be removed through the smaller access corridors achievable with the other traditional spinal approaches (e.g. posterior and postero-lateral). As an alternative, recent advances in both technology and methodology have made the lateral approach to the spine a viable surgical option. The lateral approach has proven to be a safe and effective means for performing spinal fusion and, unlike the posterior and postero-lateral approaches, the lateral approach allows for access to the disc space which is comparable to that gained through the anterior approach.
One difficulty with utilizing a lateral approach for revision surgery is the absence of the Anterior Longitudinal Ligament (ALL) which is removed during the original procedure for the anterior approach to the spine. With the ALL barrier removed, the lateral implant may be more susceptible to expulsion. A need therefore exists for interbody implants configured for insertion through a lateral approach to the spine and resistant to anterior expulsion.